The intention of the European gas industry is to enable the use of natural gas infrastructure for hydrogen. However, for the use of hydrogen in the natural gas infrastructure, the consequences or the impact of hydrogen on the gas system need to be identified. Carbon steel is the alloy family of metallic materials most used in hydrogen gas distribution pipelines, and its suitability in hydrogen gas is well studied and reported. On the contrary, studies on non-steel metallic materials also present in the current gas grid distribution networks are limited, and the effect of hydrogen embrittlement (HE) on these materials needs to be better understood.
As gas distribution networks operate at low pressure, < 16 bar, these networks are less standardised than transport networks. CANDHy project focuses on the compatibility assessment of non-steel metallic distribution gas grid materials with hydrogen in European countries.
As part of Task 2.4 of CANDHy Work Package 2, a full review of the hydrogen dissociation, solubility and diffusion in non-steel metallic materials was performed.
In this document, gaseous hydrogen dissociation and adsorption on metals, electrochemical hydrogen evolution and hydrogen diffusion are briefly described, along with the main mechanism of hydrogen embrittlement. The work focuses on hydrogen diffusion and embrittlement in cast iron, copper and lead.
Existing literature generally suggests that these materials exhibit no significant effects when exposed to high-pressure gaseous hydrogen at room temperature. However, some detrimental effects can be observed during hydrogen electrochemical charging or exposure to high-temperature H2 environments. Hydrogen embrittlement (HE) effects were observed on cast iron under cathodic polarisation. HE effects were related to the size and distribution of graphite inside the alloy, owing to their trapping effect for hydrogen. The solubility of hydrogen in copper and its alloys is very low at room temperature; thus, no detrimental effects were observed. Hydrogen molecule dissociation does not take place on lead at room temperature. If lead is polarised with very high cathodic current density in alkaline solution, lead can degrade through the formation of a volatile lead hydride.
